What are the economic reasons why the AD curve slopes down?

The aggregate demand curve represents the relationship between the overall price level in an economy and the quantity of goods and services demanded, holding all other factors constant. The AD curve slopes downward, indicating that as the price level falls (ceteris paribus), the quantity of goods and services demanded increases, and vice versa.

The real wealth effect refers to the change in consumer spending based on the perceived increase or decrease in their purchasing power due to fluctuations in the price level. As the overall price level in the economy falls, the purchasing power of people's money holdings increases. This means that their real wealth (or the amount of goods and services they can purchase with their money holdings) has increased. As a result, consumers tend to spend more, increasing the quantity of goods and services demanded. This is one reason why the AD curve slopes downward.

The interest rate effect describes the relationship between the price level and the real interest rate in the economy. When the price level decreases, the demand for money in the economy also falls, causing the nominal interest rate to decrease as well. With the nominal interest rate falling and prices being stable, the real interest rate also declines. This decline in real interest rates leads to an increase in investment spending, as borrowing becomes less expensive for both businesses and consumers. More investment spending contributes to an increase in the overall quantity of goods and services demanded, so this relationship further reinforces the downward slope of the AD curve.

The exchange rate effect describes the relationship between the price level, exchange rates, and net exports in an economy. As the price level decreases, net exports tend to increase due to domestic goods and services becoming relatively cheaper compared to foreign goods and services. This shift in relative prices leads to increased demand for domestic goods and services from both domestic and foreign consumers. As a result, the quantity of goods and services demanded in the economy increases, which contributes to the downward slope of the AD curve. In summary, the real wealth effect, interest rate effect, and exchange rate effect are the key economic reasons behind the downward slope of the aggregate demand curve. As each of these factors responds to changes in the overall price level, the quantity of goods and services demanded in the economy is directly affected, forming the downward sloping AD curve we observe in economic models.